Some of the most magnificent drawings ever executed – physical manifestations of Michelangelo's love and infatuation for a handsome and intelligent teenage boy – will on Thursday go on display as a group for the first time.

The groundbreaking show at the Courtauld gallery in London, with loans from the Vatican and the Queen, is essentially a joyously gay love story.

The drawings were done by Michelangelo when he was about 57. In the winter of 1532 the artist met ­Tommaso de' Cavalieri, a Roman nobleman celebrated for his dreamboat good looks, his superior intellect and his ­gracious manners, and fell head over heels in love with him.

Stephanie Buck, the show's curator, said it was, at heart, an extraordinary romance. "These drawings were meant to be looked at and studied, people looked at them with magnifying glasses and mirrors for hours and hours. With these drawings you can't reach higher."

The exhibition is built around The Dream of Human Life (Il Sogno, or The Dream) which was bequeathed to the Courtauld in 1978 by one of the century's most important collectors, Count Antoine Seilern. It is considered one of the finest of all Renaissance drawings. In it Michelangelo focuses on the beauty of the body, depicting a nude young man being roused from sleep, and human vices, by a winged spirit.

Buck is in no doubt The Dream is one of Michelangelo's "presentation drawings" made for Cavalieri in 1533. Others on display include The Punishment of Tityus, The Fall of Phaeton, The ­Bacchanal of Children, and The Rape of Ganymede. They would have been seen by the pope and the Medicis and on one level were teaching Cavalieri how to draw, and perhaps offering moral guidance. But they were also expressions of the artist's consuming love for the boy.

Michelangelo as an artist was at the height of his powers and fame, and almost deified. The quality is indisputable. In 1568 his biographer, Giorgio Vasari, called the works "drawings the like of which have never been seen".

Buck said it was unclear how old Cavalieri was when Michelangelo fell for him. The Courtauld research put him at between 16 and 17, she said.

The exhibition also shows that it was more than just physical infatuation. Michelangelo clearly held Cavalieri's intellect in high regard. Alongside The Fall of Phaeton is an earlier and different version on which the artist writes, saying that if the sketch does not please Cavalieri he should say so.

"The point is," said Buck, "that ­Cavalieri, although he was so young, must have played quite a role in the making of it because he was able to ­criticise it and send it back."

The Vatican has also lent for the ­exhibition ­Michelangelo's original poems, which he composed in the early stages of the friendship. Again there is little doubt as to how he felt. One reads:

"You know that I know, my lord, that you know that

I come here to enjoy you nearer at hand, and you

know that I know that you know who I really am: why

then this hesitation to greet each other, even now?

If the hope that you give me is true, if the great desire

that has been granted me is true, let the wall raised

up between these two be broken down …"

The Courtauld show is already attracting considerable academic interest, and it represents the first time that The Dream has been exhibited alongside the other presentation drawings. The last time they were together (without The Dream) was in 1988 for exhibitions in Paris and Washington.

The debate about Michelangelo and his sexuality continues. He never made any secret of his love of male beauty – just look at David – but he always maintained it was a celibate love, a platonic love. That goes, too, with Cavalieri.

Buck said: "The whole idea, which he repeats in his letters and poems, is that he doesn't want to chase Cavalieri off. He speaks of his physical desire but it is a chaste love and he is not approaching him in a manner that would make it ­difficult for Cavalieri."

Having said that, Buck believes Michelangelo was certainly gay and that he would have slept with men. But Cavalieri was from such a ­high-ranking family in papal Rome that the two of them going to bed was never going to happen. Yet Cavalieri, who later married and had children, was clearly honoured to be held so highly in the affections of Michelangelo; they stayed close friends. He was with Michelangelo at his deathbed and was later instrumental in ensuring unfinished projects were completed.

Of course the one question that wants to be answered is what did the boy look like, how handsome was he? "We know there was a portrait of Cavalieri but it is lost," said Buck. "Unfortunately."